US4439528A - Spontaneous opal glass compositions - Google Patents
Spontaneous opal glass compositions Download PDFInfo
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- US4439528A US4439528A US06/500,565 US50056583A US4439528A US 4439528 A US4439528 A US 4439528A US 50056583 A US50056583 A US 50056583A US 4439528 A US4439528 A US 4439528A
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- 239000011521 glass Substances 0.000 title claims abstract description 90
- 239000011022 opal Substances 0.000 title claims abstract description 29
- 230000002269 spontaneous effect Effects 0.000 title claims abstract description 14
- 239000000203 mixture Substances 0.000 title description 15
- 239000003513 alkali Substances 0.000 claims abstract description 28
- 239000013078 crystal Substances 0.000 claims abstract description 12
- VYPSYNLAJGMNEJ-UHFFFAOYSA-N Silicium dioxide Chemical compound O=[Si]=O VYPSYNLAJGMNEJ-UHFFFAOYSA-N 0.000 abstract description 41
- 239000000377 silicon dioxide Substances 0.000 abstract description 21
- 229910052681 coesite Inorganic materials 0.000 abstract description 19
- 229910052906 cristobalite Inorganic materials 0.000 abstract description 19
- 229910052682 stishovite Inorganic materials 0.000 abstract description 19
- 229910052905 tridymite Inorganic materials 0.000 abstract description 19
- 229910004742 Na2 O Inorganic materials 0.000 abstract description 9
- 229910018404 Al2 O3 Inorganic materials 0.000 abstract description 8
- 238000004519 manufacturing process Methods 0.000 abstract description 7
- 230000001747 exhibiting effect Effects 0.000 abstract description 2
- XLOMVQKBTHCTTD-UHFFFAOYSA-N Zinc monoxide Chemical compound [Zn]=O XLOMVQKBTHCTTD-UHFFFAOYSA-N 0.000 description 43
- 239000003599 detergent Substances 0.000 description 10
- 230000000694 effects Effects 0.000 description 8
- 238000000034 method Methods 0.000 description 8
- 238000012360 testing method Methods 0.000 description 8
- KRHYYFGTRYWZRS-UHFFFAOYSA-M Fluoride anion Chemical compound [F-] KRHYYFGTRYWZRS-UHFFFAOYSA-M 0.000 description 7
- 208000016261 weight loss Diseases 0.000 description 7
- 230000004580 weight loss Effects 0.000 description 7
- GWEVSGVZZGPLCZ-UHFFFAOYSA-N Titan oxide Chemical compound O=[Ti]=O GWEVSGVZZGPLCZ-UHFFFAOYSA-N 0.000 description 6
- 238000005191 phase separation Methods 0.000 description 6
- 238000007792 addition Methods 0.000 description 5
- 229910052731 fluorine Inorganic materials 0.000 description 5
- 239000000155 melt Substances 0.000 description 5
- 239000000243 solution Substances 0.000 description 5
- YCKRFDGAMUMZLT-UHFFFAOYSA-N Fluorine atom Chemical compound [F] YCKRFDGAMUMZLT-UHFFFAOYSA-N 0.000 description 4
- 229910052783 alkali metal Inorganic materials 0.000 description 4
- 150000001340 alkali metals Chemical class 0.000 description 4
- 150000001768 cations Chemical class 0.000 description 4
- 239000011737 fluorine Substances 0.000 description 4
- 239000000463 material Substances 0.000 description 4
- 230000007246 mechanism Effects 0.000 description 4
- BASFCYQUMIYNBI-UHFFFAOYSA-N platinum Chemical compound [Pt] BASFCYQUMIYNBI-UHFFFAOYSA-N 0.000 description 4
- 230000009467 reduction Effects 0.000 description 4
- 229910000831 Steel Inorganic materials 0.000 description 3
- 230000002411 adverse Effects 0.000 description 3
- 229910000287 alkaline earth metal oxide Inorganic materials 0.000 description 3
- 239000006121 base glass Substances 0.000 description 3
- WUKWITHWXAAZEY-UHFFFAOYSA-L calcium difluoride Chemical compound [F-].[F-].[Ca+2] WUKWITHWXAAZEY-UHFFFAOYSA-L 0.000 description 3
- 229910001634 calcium fluoride Inorganic materials 0.000 description 3
- 230000006872 improvement Effects 0.000 description 3
- 239000010959 steel Substances 0.000 description 3
- 239000000126 substance Substances 0.000 description 3
- OGIDPMRJRNCKJF-UHFFFAOYSA-N titanium oxide Inorganic materials [Ti]=O OGIDPMRJRNCKJF-UHFFFAOYSA-N 0.000 description 3
- 229910004865 K2 O Inorganic materials 0.000 description 2
- 229910011763 Li2 O Inorganic materials 0.000 description 2
- HCHKCACWOHOZIP-UHFFFAOYSA-N Zinc Chemical compound [Zn] HCHKCACWOHOZIP-UHFFFAOYSA-N 0.000 description 2
- MCMNRKCIXSYSNV-UHFFFAOYSA-N Zirconium dioxide Chemical compound O=[Zr]=O MCMNRKCIXSYSNV-UHFFFAOYSA-N 0.000 description 2
- 229910052784 alkaline earth metal Inorganic materials 0.000 description 2
- 150000001342 alkaline earth metals Chemical class 0.000 description 2
- 238000000149 argon plasma sintering Methods 0.000 description 2
- 230000015572 biosynthetic process Effects 0.000 description 2
- 229910052918 calcium silicate Inorganic materials 0.000 description 2
- 239000000378 calcium silicate Substances 0.000 description 2
- OYACROKNLOSFPA-UHFFFAOYSA-N calcium;dioxido(oxo)silane Chemical compound [Ca+2].[O-][Si]([O-])=O OYACROKNLOSFPA-UHFFFAOYSA-N 0.000 description 2
- 239000003795 chemical substances by application Substances 0.000 description 2
- 238000001816 cooling Methods 0.000 description 2
- 239000004744 fabric Substances 0.000 description 2
- YBMRDBCBODYGJE-UHFFFAOYSA-N germanium dioxide Chemical compound O=[Ge]=O YBMRDBCBODYGJE-UHFFFAOYSA-N 0.000 description 2
- 238000007496 glass forming Methods 0.000 description 2
- 238000007654 immersion Methods 0.000 description 2
- 239000011159 matrix material Substances 0.000 description 2
- 238000005259 measurement Methods 0.000 description 2
- 238000002156 mixing Methods 0.000 description 2
- 239000002245 particle Substances 0.000 description 2
- 229910052697 platinum Inorganic materials 0.000 description 2
- 238000006467 substitution reaction Methods 0.000 description 2
- 239000000725 suspension Substances 0.000 description 2
- 229910052725 zinc Inorganic materials 0.000 description 2
- 239000011701 zinc Substances 0.000 description 2
- 229910016264 Bi2 O3 Inorganic materials 0.000 description 1
- ZOXJGFHDIHLPTG-UHFFFAOYSA-N Boron Chemical compound [B] ZOXJGFHDIHLPTG-UHFFFAOYSA-N 0.000 description 1
- FYYHWMGAXLPEAU-UHFFFAOYSA-N Magnesium Chemical compound [Mg] FYYHWMGAXLPEAU-UHFFFAOYSA-N 0.000 description 1
- 229910019639 Nb2 O5 Inorganic materials 0.000 description 1
- 238000010521 absorption reaction Methods 0.000 description 1
- 229910000272 alkali metal oxide Inorganic materials 0.000 description 1
- 229910052915 alkaline earth metal silicate Inorganic materials 0.000 description 1
- 238000004458 analytical method Methods 0.000 description 1
- 238000013459 approach Methods 0.000 description 1
- 239000007864 aqueous solution Substances 0.000 description 1
- QVQLCTNNEUAWMS-UHFFFAOYSA-N barium oxide Inorganic materials [Ba]=O QVQLCTNNEUAWMS-UHFFFAOYSA-N 0.000 description 1
- 230000009286 beneficial effect Effects 0.000 description 1
- 229910002056 binary alloy Inorganic materials 0.000 description 1
- 229910052796 boron Inorganic materials 0.000 description 1
- CETPSERCERDGAM-UHFFFAOYSA-N ceric oxide Chemical compound O=[Ce]=O CETPSERCERDGAM-UHFFFAOYSA-N 0.000 description 1
- 229910000422 cerium(IV) oxide Inorganic materials 0.000 description 1
- 230000008859 change Effects 0.000 description 1
- 239000003086 colorant Substances 0.000 description 1
- 150000001875 compounds Chemical class 0.000 description 1
- 239000000470 constituent Substances 0.000 description 1
- 230000007797 corrosion Effects 0.000 description 1
- 238000005260 corrosion Methods 0.000 description 1
- 230000002939 deleterious effect Effects 0.000 description 1
- 238000004851 dishwashing Methods 0.000 description 1
- 238000000635 electron micrograph Methods 0.000 description 1
- 239000006066 glass batch Substances 0.000 description 1
- 239000004615 ingredient Substances 0.000 description 1
- 208000020442 loss of weight Diseases 0.000 description 1
- 229910052749 magnesium Inorganic materials 0.000 description 1
- 239000011777 magnesium Substances 0.000 description 1
- 230000014759 maintenance of location Effects 0.000 description 1
- 229910044991 metal oxide Inorganic materials 0.000 description 1
- 150000004706 metal oxides Chemical class 0.000 description 1
- 230000002688 persistence Effects 0.000 description 1
- 239000000843 powder Substances 0.000 description 1
- 238000003825 pressing Methods 0.000 description 1
- 230000008569 process Effects 0.000 description 1
- 230000002035 prolonged effect Effects 0.000 description 1
- 238000009877 rendering Methods 0.000 description 1
- 238000012216 screening Methods 0.000 description 1
- 230000035939 shock Effects 0.000 description 1
- 239000005368 silicate glass Substances 0.000 description 1
- 238000010186 staining Methods 0.000 description 1
- 239000008399 tap water Substances 0.000 description 1
- 235000020679 tap water Nutrition 0.000 description 1
Classifications
-
- C—CHEMISTRY; METALLURGY
- C03—GLASS; MINERAL OR SLAG WOOL
- C03C—CHEMICAL COMPOSITION OF GLASSES, GLAZES OR VITREOUS ENAMELS; SURFACE TREATMENT OF GLASS; SURFACE TREATMENT OF FIBRES OR FILAMENTS MADE FROM GLASS, MINERALS OR SLAGS; JOINING GLASS TO GLASS OR OTHER MATERIALS
- C03C3/00—Glass compositions
- C03C3/04—Glass compositions containing silica
- C03C3/076—Glass compositions containing silica with 40% to 90% silica, by weight
- C03C3/083—Glass compositions containing silica with 40% to 90% silica, by weight containing aluminium oxide or an iron compound
- C03C3/085—Glass compositions containing silica with 40% to 90% silica, by weight containing aluminium oxide or an iron compound containing an oxide of a divalent metal
- C03C3/087—Glass compositions containing silica with 40% to 90% silica, by weight containing aluminium oxide or an iron compound containing an oxide of a divalent metal containing calcium oxide, e.g. common sheet or container glass
-
- C—CHEMISTRY; METALLURGY
- C03—GLASS; MINERAL OR SLAG WOOL
- C03C—CHEMICAL COMPOSITION OF GLASSES, GLAZES OR VITREOUS ENAMELS; SURFACE TREATMENT OF GLASS; SURFACE TREATMENT OF FIBRES OR FILAMENTS MADE FROM GLASS, MINERALS OR SLAGS; JOINING GLASS TO GLASS OR OTHER MATERIALS
- C03C3/00—Glass compositions
- C03C3/04—Glass compositions containing silica
- C03C3/076—Glass compositions containing silica with 40% to 90% silica, by weight
- C03C3/078—Glass compositions containing silica with 40% to 90% silica, by weight containing an oxide of a divalent metal, e.g. an oxide of zinc
-
- C—CHEMISTRY; METALLURGY
- C03—GLASS; MINERAL OR SLAG WOOL
- C03C—CHEMICAL COMPOSITION OF GLASSES, GLAZES OR VITREOUS ENAMELS; SURFACE TREATMENT OF GLASS; SURFACE TREATMENT OF FIBRES OR FILAMENTS MADE FROM GLASS, MINERALS OR SLAGS; JOINING GLASS TO GLASS OR OTHER MATERIALS
- C03C3/00—Glass compositions
- C03C3/04—Glass compositions containing silica
- C03C3/076—Glass compositions containing silica with 40% to 90% silica, by weight
- C03C3/11—Glass compositions containing silica with 40% to 90% silica, by weight containing halogen or nitrogen
- C03C3/112—Glass compositions containing silica with 40% to 90% silica, by weight containing halogen or nitrogen containing fluorine
-
- C—CHEMISTRY; METALLURGY
- C03—GLASS; MINERAL OR SLAG WOOL
- C03C—CHEMICAL COMPOSITION OF GLASSES, GLAZES OR VITREOUS ENAMELS; SURFACE TREATMENT OF GLASS; SURFACE TREATMENT OF FIBRES OR FILAMENTS MADE FROM GLASS, MINERALS OR SLAGS; JOINING GLASS TO GLASS OR OTHER MATERIALS
- C03C4/00—Compositions for glass with special properties
- C03C4/005—Compositions for glass with special properties for opaline glass
Definitions
- Opacity in glasses is normally achieved through one of two mechanisms or as a result of a combination of those two mechanisms.
- the first means of light scattering involves the presence of a small amount of material suspended in the glass which has an index of refraction differing very markedly from that of the base glass phase.
- the phases present may differ less in index, but where the suspended phase constitutes a major proportion of the body, the high number of interfaces occurring gives rise to extensive light scattering with consequent opacity.
- Either mechanism may involve suspensions of crystals in a glassy matrix or suspensions comprising two immiscible glassy phases.
- Opal glasses have also been classified by the glass manufacturer according to the method of production. For example, where the kinetics of phase separation are so rapid that opacity occurs during the quick cooling of a glass body characteristic of the conventional glass forming processes, spontaneous opals are stated to result. In contrast, where the kinetics of phase separation are so slow that the glass body must be maintained for a substantial length of time within a temperature interval wherein phase separation takes place at a finite rate, the resultant products are termed reheat or thermally opacifiable opals. As can be readily appreciated, the need for a separate heat treating step significantly increases the production cost of reheat opal glasses.
- the primary objective of the present invention is to provide an opal glass demonstrating a very high degree of opacity suitable for use as dinnerware. That utility impresses several constraints upon the character and means of production of the glass. To illustrate, the operable compositions will form spontaneous opals so that the expense of special heat treating procedures to secure the desired opacity will be eliminated.
- the glass must resist chemical attack by alkalies present in commonly used dishwashing materials. Prolonged and/or repeated exposure of the glass must neither remove the gloss from the surface of the dish nor cause a degree of porosity in the surface which can result in the absorption of foreign substances with consequent staining. Most preferably, the glass will be compatible with currently conventional decorating techniques.
- the crystal liquidus temperature will be less than 1350° C. by as large an increment as possible.
- any inclusion of fluorine will be in small amounts, viz., less than 5% by weight.
- fluorine is relatively volatile and, hence, pollutes the air to a certain extent, it is preferred that the fluorine level be held as low as possible, ideally zero.
- the viscosity of the glass at the liquidus temperature will exceed 200 poises.
- alkaline earth metal silicate glasses can exhibit very dense opacities because of the very broad regions of immiscibility in the binary systems.
- the present invention is founded in my discovery that the addition of zinc to calcium silicate opal glass compositions markedly enhances the chemical durability thereof. Whereas previous researchers have disclosed useful opal glasses containing silica and the alkaline earths, those glasses are unlike the products of the instant invention either because they owe their opacity to calcium fluoride crystals and are not as opaque as the present glasses, or because they contain appreciable amounts of boron and do not display the desired durability.
- compositions yield spontaneous opal glasses of dense opacity, excellent resistance to attack by alkalies such as are found in dishwasher detergents, coefficients of thermal expansion (25°-300° C.) between about 60-90 ⁇ 10 -7 /°C., softening points in excess of 750° C., crystal liquidus temperatures below 1350° C., liquidus viscosities in excess of 200 poises, and wherein the opacity results from spherically-shaped droplets of an immiscible glassy phase having diameters of less than one micron.
- the opacifying agents include one or more of BaO, CaO, CoO, CuO, MgO, MnO, NiO, and ZnO. There is no definition of the character of the opacifying phase; the text merely alludes to diffusing particles.
- U.S. Pat. No. 3,661,601 is directed to the manufacture of spontaneous opal glasses wherein the opacity is caused by the presence of fluoride-containing droplets of an immiscible glassy phase.
- the glasses consist essentially, in weight percent, of:
- Up to 10% total of at least one oxide of the following group may optionally be included: BaO, Bi 2 O 3 , CeO 2 O, GeO 2 , La 2 O 3 , Nb 2 O 5 , P 2 O 5 , PbO, SrO, TiO 2 , and ZnO.
- U.S. Pat. No. 3,681,098 is drawn to the formation of spontaneous opal glasses wherein the opacity is generated through the presence of fluoride-containing droplets of an immiscible glassy phase and CaF 2 crystals.
- the glasses consist essentially, in weight percent, of:
- At least one oxide of the following group may optionally be included: B 2 O 3 , BaO, MgO, P 2 O 5 , PbO, SrO, TiO 2 , ZnO, and ZrO 2 .
- U.S. Pat. No. 4,311,529 discloses the tinting of spontaneous opal glasses wherein CaF 2 crystals constitute the opacifying phase.
- the base glass compositions consist essentially, in weight percent, of:
- RO consists of at least one oxide from the group BaO, CaO, MgO, SrO, and ZnO
- R 2 O consists of at least one oxide from the group of Li 2 O, Na 2 O, and K 2 O.
- CaO comprises at least 60% of the RO content
- Na 2 O comprises at least 75% of the R 2 O content.
- Tables I-XIII report examples of glass compositions, expressed in terms of parts by weight on the oxide basis, illustrating the parameters of the present invention. Inasmuch as the sum of the tabulated components totals or approximately totals 100, for all practical purposes the individual values of the recorded constituents may be deemed to reflect weight percent. In accordance with conventional glass analysis practice, where fluorine was utilized in the glass batch materials, it is recited as the entity, fluoride, since it is not known with which cation it is bonded. Tables IA-XIIIA report the compositions in terms of cation percent. In certain instances comparisons of compositional variations becomes more clear when viewed on a cation basis than on a simple weight percent basis. The actual ingredients for the glass batches may comprise any materials, either oxides or other compounds, which, when melted together, will be converted into the desired oxides in the proper proportions.
- the solution is heated to 95° C. and samples of the glass immersed therein, the surface area of the samples being limited by the ratio of 12 square inches to one pound of the solution.
- the samples are withdrawn from the solution at 24-hour intervals up to 96 hours, rinsed in tap water, and wiped dry. The gloss of each sample was compared visually to reference samples.
- the porosity induced in the glass through attack by the alkalies present in the detergent was determined in the following manner.
- Tables I and IA illustrate spontaneous opal glass compositions in the CaO-Al 2 O 3 -B 2 O 3 -SiO 2 system of the type known to the prior art.
- the weight loss data unequivocally demonstrate the poor resistance to alkalies exhibited by those glasses, thereby rendering them unsuitable for tableware.
- Tables II and IIA reveal that the replacement of SiO 2 by ZnO improves the resistance of calcium silicate opal glasses to attack by alkalies.
- An examination of Examples 11-13 evidences a similar effect in glasses containing Na 2 O. Those Examples also dramatize the profound difference in resistance to alkali attack between replacing SiO 2 with ZnO and replacing SiO 2 with additional CaO.
- Examples 11-13 further illustrate that ZnO does not adversely affect the kinetics of opal information. At high temperatures ZnO appears to suppress phase separation, but during rapid cooling the opal phase "strikes in" at a very convenient temperature.
- Tables III and IIIA manifest that, in spite of its similarity in size and charge to zinc, the inclusion of magnesium does not impart an equal improvement in alkali resistance to the glasses.
- Tables V and VA indicate that high levels of ZnO enhance the resistance of the glasses to alkali attack even at relatively low SiO 2 values. Moreover, in glasses containing such low levels of SiO 2 , ZnO not only improves the alkali resistance thereof but also the density of opacity. Nevertheless, it must be noted that the inclusion of fluoride in glasses of low silica contents deleteriously affects the alkali resistance of such glasses even when high levels of ZnO are present.
- Tables VI and VIA illustrate the flexibility available in adjusting the content of alkali metal and/or alkaline earth metal to increase the coefficient of thermal expansion of the glass with minimal effect upon alkali resistance. For example, a slight increase in the level of CaO at the expense of SiO 2 raises the expansion coefficient with only a slight reduction in alkali resistance. Unfortunately, a concomitant effect is a sacrifice in the density of the opacity. Opal density can be restored, however, through the addition of fluoride. And because of the high SiO 2 contents of the glasses, this addition of fluoride does not have a markedly adverse effect upon alkali resistance.
- Tables VII and VIIA and Tables VIII and VIIIA provide further illustrations of varying the alkali metal contents of the glasses to yield articles of acceptable resistance to alkalies.
- Li 2 O can replace part of the SiO 2 without undue reduction in alkali resistance.
- K 2 O can be utilized as part of the alkali metal content and its use appears to enhance the alkali resistance of the glass. Nevertheless, its effect upon phase separation is very profound such that the restoration of opacity demands greater fluoride levels than are desirable.
- Tables IX and IXA show that replacing CaO with ZnO causes a reduction in the coefficient of thermal expansion of the glass as well as improving the alkali resistance thereof as has been illustrated above.
- Tables X and XA disclose that a small amount of Al 2 O 3 can lead to a marked improvement in alkali resistance.
- a comparison of Example 39 with Example 40 clearly evidences a significant improvement in alkali resistance when Al 2 O 3 is substituted for SiO 2 .
- a similar effect occurs when Al 2 O 3 replaces some SiO 2 and alkali metal oxide, as is demonstrated through a comparison of Example 41 with Example 39.
- Examples 12 and 31 manifest a fivefold reduction in weight loss when Al 2 O 3 is substituted for Na 2 O and CaO, and the SiO 2 value is maintained constant.
- Tables XI and XIA are designed to demonstrate the correlation which exists between the weight loss measurements and the above-described detergent test. Thus, glasses exhibiting a weight loss of 0.08 mg/cm 2 will sometimes demonstrate an "A" rating in the stain test.
- the loss of gloss observed on the top surface of the samples and the retention of gloss seen on the bottom surface of the samples can be explained in the following manner.
- the bottom refers to the surface of the sample which contacts the steel plate onto which the melt is poured to form glass patties. This surface is analogous to and would be expected to manifest properties similar to those noted on the surface of glass articles formed via a pressing operation.
- the top surface cools slowly and is conjectured to have associated with it an exceptionally coarse phase separation.
- Tables XII and XIIA illustrate studies undertaken to investigate means for achieving a lower crystal liquidus temperature in the subject glasses without harming the alkali resistance thereof.
- the exemplary compositions reported demonstrate the effect resulting from mixing the alkaline earth metal oxides. As is evident, any decrease in liquidus temperature attributed to the entropy of mixing, when the alkaline earth metal oxides are combined, is virtually negligible compared to the direct influence of the ionic size of the individual alkaline earth metals. It should also be noted that the viscosity of the glasses tends to become independent of composition at very high temperatures. Consequently, any change in composition which reduces the liquidus temperature automatically increases the viscosity of the glass at the liquidus.
- Example 52 exhibits a desirably low liquidus temperature and high liquidus viscosity but, unfortunately, has unsatisfactory alkali resistance.
- ZnO can be added to improve alkali resistance but, as manifested in Table IV above, ZnO raises the liquidus temperature.
- Tables XIII and XIIIA point out that not only does the substitution of TiO 2 for SiO 2 not reduce the crystal liquidus temperature, but also that the substitution introduces color into the opal glass.
- the replacement of SiO 2 with B 2 O 3 or P 2 O 5 does not appear to endow the final glass with any advantageous properties.
- the more preferred glasses will consist essentially, expressed in terms of weight percent on the oxide basis, of 60-70% SiO 2 , 20-30% CaO, 5-15% ZnO, 1.5-4% Na 2 O, 0-2% Al 2 O 3 , and 0-3% F.
- Example 12 is deemed to be the most preferred composition. Electron micrographs of that glass in the opal state demonstrate that spherical amorphous droplets no larger than about 0.5 micron impart the opacity. Such small droplets will not constitute stress concentrating sites. Inasmuch as the alkali metal content of the inventive glasses is low, products made therefrom are quite useful in microwave applications.
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- Chemical & Material Sciences (AREA)
- Life Sciences & Earth Sciences (AREA)
- Engineering & Computer Science (AREA)
- Chemical Kinetics & Catalysis (AREA)
- General Chemical & Material Sciences (AREA)
- Geochemistry & Mineralogy (AREA)
- Materials Engineering (AREA)
- Organic Chemistry (AREA)
- Glass Compositions (AREA)
Abstract
The present invention is directed to the production of spontaneous opal glasses exhibiting softening points in excess of 750° C., a coefficient of thermal expansion between about 60-90×10-7 /°C., a crystal liquidus temperature below 1350° C., a liquidus viscosity of at least 200 poises, and excellent resistance to attack by alkalies. Spherically-shaped glassy droplets constitute the opal phase in the glasses which consist essentially, in weight percent, of
______________________________________
SiO2
50-72 Na2 O
0-8
CaO 10-40 Al2 O3
0-2
ZnO 4-40 F 0-5
______________________________________
Description
A glass comprised of two or more finely-dispersed phases of differing refractive indices scatters an appreciable quantity of visible light. When in sufficient thickness such glasses can exhibit complete opacity even though they absorb virtually no visible light. Such glasses, termed opals, are well known in the glass industry for the fabrication of products as diverse as lantern globes and dinner dishes.
Opacity in glasses is normally achieved through one of two mechanisms or as a result of a combination of those two mechanisms. The first means of light scattering involves the presence of a small amount of material suspended in the glass which has an index of refraction differing very markedly from that of the base glass phase. In the second mechanism the phases present may differ less in index, but where the suspended phase constitutes a major proportion of the body, the high number of interfaces occurring gives rise to extensive light scattering with consequent opacity. Either mechanism may involve suspensions of crystals in a glassy matrix or suspensions comprising two immiscible glassy phases.
Opal glasses have also been classified by the glass manufacturer according to the method of production. For example, where the kinetics of phase separation are so rapid that opacity occurs during the quick cooling of a glass body characteristic of the conventional glass forming processes, spontaneous opals are stated to result. In contrast, where the kinetics of phase separation are so slow that the glass body must be maintained for a substantial length of time within a temperature interval wherein phase separation takes place at a finite rate, the resultant products are termed reheat or thermally opacifiable opals. As can be readily appreciated, the need for a separate heat treating step significantly increases the production cost of reheat opal glasses.
The primary objective of the present invention is to provide an opal glass demonstrating a very high degree of opacity suitable for use as dinnerware. That utility impresses several constraints upon the character and means of production of the glass. To illustrate, the operable compositions will form spontaneous opals so that the expense of special heat treating procedures to secure the desired opacity will be eliminated. The glass must resist chemical attack by alkalies present in commonly used dishwashing materials. Prolonged and/or repeated exposure of the glass must neither remove the gloss from the surface of the dish nor cause a degree of porosity in the surface which can result in the absorption of foreign substances with consequent staining. Most preferably, the glass will be compatible with currently conventional decorating techniques. That circumstance demands a coefficient of thermal expansion of between about 60-90×10-7 /°C. and a softening point in excess of 750° C. Furthermore, it is highly desirable that the glass not be excessively heated when used in a microwave oven. Inasmuch as occlusions having diameters no larger than 75 microns can initiate breakage when the glass article is exposed to thermal shock, the particles suspended in the base glass matrix must not approach that size.
In order to forestall excessive corrosion of the molds used in the formation of glass article, the crystal liquidus temperature will be less than 1350° C. by as large an increment as possible. For the same reason, any inclusion of fluorine will be in small amounts, viz., less than 5% by weight. Moreover, because fluorine is relatively volatile and, hence, pollutes the air to a certain extent, it is preferred that the fluorine level be held as low as possible, ideally zero. For convenience in forming glass articles, the viscosity of the glass at the liquidus temperature will exceed 200 poises.
It is well known in the glass art that in numerous instances alkaline earth metal silicate glasses can exhibit very dense opacities because of the very broad regions of immiscibility in the binary systems. The present invention is founded in my discovery that the addition of zinc to calcium silicate opal glass compositions markedly enhances the chemical durability thereof. Whereas previous researchers have disclosed useful opal glasses containing silica and the alkaline earths, those glasses are unlike the products of the instant invention either because they owe their opacity to calcium fluoride crystals and are not as opaque as the present glasses, or because they contain appreciable amounts of boron and do not display the desired durability.
I have found that the above objective can be achieved with glass compositions consisting essentially, expressed in terms of weight percent on the oxide basis, of about
______________________________________
SiO.sub.2
50-72
CaO 10-40
ZnO 4-40
Na.sub.2 O
0-8
Al.sub.2 O.sub.3
0-2
F 0-5
______________________________________
Such compositions yield spontaneous opal glasses of dense opacity, excellent resistance to attack by alkalies such as are found in dishwasher detergents, coefficients of thermal expansion (25°-300° C.) between about 60-90×10-7 /°C., softening points in excess of 750° C., crystal liquidus temperatures below 1350° C., liquidus viscosities in excess of 200 poises, and wherein the opacity results from spherically-shaped droplets of an immiscible glassy phase having diameters of less than one micron.
U.S. Pat. No. 3,275,492 describes the production of spontaneous and reheat opal glasses of borosilicate-based compositions consisting essentially, in mole percent, of:
______________________________________
SiO.sub.2 66-81
B.sub.2 O.sub.3 10-27
Li.sub.2 O and/or Na.sub.2 O and/or K.sub.2 O
1-7
Al.sub.2 O.sub.3 0-1
Opacifying Agents 3-24
______________________________________
The opacifying agents include one or more of BaO, CaO, CoO, CuO, MgO, MnO, NiO, and ZnO. There is no definition of the character of the opacifying phase; the text merely alludes to diffusing particles.
U.S. Pat. No. 3,661,601 is directed to the manufacture of spontaneous opal glasses wherein the opacity is caused by the presence of fluoride-containing droplets of an immiscible glassy phase. The glasses consist essentially, in weight percent, of:
______________________________________
SiO.sub.2
50-75 Na.sub.2 O 0-7
Al.sub.2 O
3-9 K.sub.2 O 0-7
CaO 11-20 Na.sub.2 O + K.sub.2 O
3-10
B.sub.2 O.sub.3
1-7 F 2-4
______________________________________
Up to 10% total of at least one oxide of the following group may optionally be included: BaO, Bi2 O3, CeO2 O, GeO2, La2 O3, Nb2 O5, P2 O5, PbO, SrO, TiO2, and ZnO.
U.S. Pat. No. 3,681,098 is drawn to the formation of spontaneous opal glasses wherein the opacity is generated through the presence of fluoride-containing droplets of an immiscible glassy phase and CaF2 crystals. The glasses consist essentially, in weight percent, of:
______________________________________
SiO.sub.2 50-75
Al.sub.2 O.sub.3 3-14
CaO 10-20
Na.sub.2 O 0-7
K.sub.2 O 0-7
Na.sub.2 O + K.sub.2 O
3-10
MoO.sub.3 and/or WO.sub.3 and/or As.sub.2 O.sub.3
0.25-5
F 2-5
______________________________________
Up to 10% total of at least one oxide of the following group may optionally be included: B2 O3, BaO, MgO, P2 O5, PbO, SrO, TiO2, ZnO, and ZrO2.
U.S. Pat. No. 4,311,529 discloses the tinting of spontaneous opal glasses wherein CaF2 crystals constitute the opacifying phase. The base glass compositions consist essentially, in weight percent, of:
______________________________________
SiO.sub.2
57-61 ZnO 8-10
Al.sub.2 O.sub.3
10-11 Na.sub.2 O
8-9
B.sub.2 O.sub.3
1-2 K.sub.2 O
2-2.5
CaO 5-6.5 F 3-4
______________________________________
British Pat. No. 1,315,828 cites spontaneous borosilicate-based opal glasses wherein an unidentified immiscible glassy phase gives rise to the opacity. The glasses consist essentially, in weight percent, of:
______________________________________
SiO.sub.2
60-75 Al.sub.2 O.sub.3
2-7
B.sub.2 O.sub.3
8-15 ZrO.sub.2
0-2.5
RO 9-17 TiO.sub.2
0-4
R.sub.2 O
3-7 F 1-4
______________________________________
RO consists of at least one oxide from the group BaO, CaO, MgO, SrO, and ZnO, and R2 O consists of at least one oxide from the group of Li2 O, Na2 O, and K2 O. In the preferred glasses CaO comprises at least 60% of the RO content and Na2 O comprises at least 75% of the R2 O content.
Tables I-XIII report examples of glass compositions, expressed in terms of parts by weight on the oxide basis, illustrating the parameters of the present invention. Inasmuch as the sum of the tabulated components totals or approximately totals 100, for all practical purposes the individual values of the recorded constituents may be deemed to reflect weight percent. In accordance with conventional glass analysis practice, where fluorine was utilized in the glass batch materials, it is recited as the entity, fluoride, since it is not known with which cation it is bonded. Tables IA-XIIIA report the compositions in terms of cation percent. In certain instances comparisons of compositional variations becomes more clear when viewed on a cation basis than on a simple weight percent basis. The actual ingredients for the glass batches may comprise any materials, either oxides or other compounds, which, when melted together, will be converted into the desired oxides in the proper proportions.
Batches of about 800 grams were compounded, thoroughly mixed together, and charged into platinum crucibles. After covering, the crucibles were introduced into a furnace operating at about 1600° C. and the batches melted for about six hours. Part of the melt was run through steel rollers to form thin ribbon, i.e., glass ribbon having a thickness of about 0.5 mm, to determine the opacity generated in a glass forming operation involving rapid chilling. The remainder of the melt was poured onto a steel plate to produce a generally rectangular glass patty which was then immediately transferred to an annealer operating at about 650° C.
Small samples of the glasses were placed into thin platinum boats through which an electrical current was passed to melt the glass. When the current is turned off, the melt cools very rapidly. This practice permits the temperature at which opalization occurs, also known as the opal liquidus (op. liq.), to be measured utilizing laser reflectance techniques.
The following procedure was devised to evaluate the resistance of the inventive opal glasses to commercial dishwasher detergents. A 0.3% by weight aqueous solution of SUPER SOILAX® detergent, manufactured by Economics Laboratories, St. Paul, Minn., is prepared. The solution is heated to 95° C. and samples of the glass immersed therein, the surface area of the samples being limited by the ratio of 12 square inches to one pound of the solution. The samples are withdrawn from the solution at 24-hour intervals up to 96 hours, rinsed in tap water, and wiped dry. The gloss of each sample was compared visually to reference samples. The porosity induced in the glass through attack by the alkalies present in the detergent was determined in the following manner. A drop of SPOTCHECK® dye penetrant, marketed by Magnaflux Corporation, Chicago, Ill., was allowed to stand on the glass surface for 20 seconds. If the coloration could be completely removed by wiping the surface with a cloth moistened with the above SUPER SOILAX® detergent solution, the sample was rated "A". If the coloration could be completely removed after rubbing the surface with a cloth and a household cleansing powder for about 30 seconds, the sample was rated "B". Persistence of the stain after this latter treatment results in the sample being rated "C". To be deemed acceptable, the glass must show no loss of gloss and be rated "A" after an exposure to the detergent of 96 hours.
Although the above-identified test comprises the ultimate criterion for the acceptable utility of an opal glass for dinnerware, its qualitative character does not provide the researcher with a screening procedure for relatively rapidly detecting minor differences between samples. Therefore, a quantitative measure of resistance to alkalies was devised via the determination of the loss of weight (mg/cm2) experienced by a sample after an immersion for six hours in an aqueous 0.2 N solution of Na2 CO3 maintained at 95° C. A weight loss (wt. loss) of no more than 0.1 mg/cm2 has been found acceptable with the preferred maximum being no more than 0.05 mg/cm2.
Measurements of softening point (S.P.) in °C., coefficient of thermal expansion (Exp.) over the range of 25°-300° C. in terms of ×10-7 /°C., crystal liquidus (cry. liq.) in °C., and the viscosity (vis.) of the glass at its crystal liquidus in terms of poises were conducted in accordance wit techniques conventional in the glass art. Opal density (Op. Den.) was evaluated visually.
Tables I and IA illustrate spontaneous opal glass compositions in the CaO-Al2 O3 -B2 O3 -SiO2 system of the type known to the prior art. The weight loss data unequivocally demonstrate the poor resistance to alkalies exhibited by those glasses, thereby rendering them unsuitable for tableware.
TABLE I
______________________________________
1 2 3 4 5 6 7
______________________________________
SiO.sub.2
67.6 68.1 68.5 63.3 62.6 63.0 63.5
Al.sub.2 O.sub.3
6.62 4.44 2.24 8.95 6.64 4.46 2.24
B.sub.2 O.sub.3
1.51 3.03 4.58 3.06 1.51 3.04 4.60
CaO 24.3 24.4 24.6 24.6 29.2 29.4 29.6
mg/cm.sup.2
0.16 0.25 0.37 0.17 0.19 0.25 0.36
______________________________________
TABLE IA
______________________________________
1 2 3 4 5 6 7
______________________________________
SiO.sub.2
65.0 65.0 65.0 60.0 60.0 60.0 60.0
Al.sub.2 O.sub.3
7.5 5.0 2.5 10.0 7.5 5.0 2.4
B.sub.2 O.sub.3
2.5 5.0 7.5 5.0 2.4 5.0 7.5
CaO 25.0 25.0 25.0 25.0 30.0 30.0 30.0
______________________________________
Tables II and IIA reveal that the replacement of SiO2 by ZnO improves the resistance of calcium silicate opal glasses to attack by alkalies. An examination of Examples 11-13 evidences a similar effect in glasses containing Na2 O. Those Examples also dramatize the profound difference in resistance to alkali attack between replacing SiO2 with ZnO and replacing SiO2 with additional CaO. Finally, Examples 11-13 further illustrate that ZnO does not adversely affect the kinetics of opal information. At high temperatures ZnO appears to suppress phase separation, but during rapid cooling the opal phase "strikes in" at a very convenient temperature.
TABLE II
______________________________________
8 9 10 11 12 13
______________________________________
SiO.sub.2
64.5 60.8 57.1 72.9 66.5 67.9
CaO 35.4 35.0 34.6 24.3 23.9 29.3
ZnO -- 4.12 8.14 -- 6.93 --
Na.sub.2 O
-- -- -- 2.69 2.64 2.69
mg/cm.sup.2
0.24 0.09 0.06 0.23 0.05 0.24
Op. Liq.
-- -- -- 1400 1140 1200
Cry. Liq.
-- -- -- 1365 1300 1360
______________________________________
TABLE IIA
______________________________________
8 9 10 11 12 13
______________________________________
SiO.sub.2
63 60 57 70 65 65
CaO 37 37 37 25 25 30
ZnO -- 3 6 -- 5 --
Na.sub.2 O
-- -- -- 5 5 5
______________________________________
Tables III and IIIA manifest that, in spite of its similarity in size and charge to zinc, the inclusion of magnesium does not impart an equal improvement in alkali resistance to the glasses.
TABLE III
______________________________________
14 15 16 17
______________________________________
SiO.sub.2 66.3 68.9 66.5 68.9
CaO 23.8 24.7 22.9 23.7
ZnO 6.91 -- 6.92 --
MgO -- 3.55 -- 3.55
Na.sub.2 O 2.50 2.60 2.37 2.46
Al.sub.2 O.sub.3
0.217 0.23 1.30 1.35
mg/cm.sup.2 0.05 0.22 0.01 0.21
______________________________________
TABLE IIIA
______________________________________
14 15 16 17
______________________________________
SiO.sub.2 65.0 65.0 65.0 65.0
CaO 25.0 25.0 24.0 24.0
ZnO 5.0 -- 5.0 --
MgO -- 5.0 -- 5.0
Na.sub.2 O 4.75 4.75 4.5 4.5
Al.sub.2 O.sub.3
0.25 0.25 1.5 1.5
______________________________________
That the beneficial effect upon alkali resistance exerted by ZnO is not limited to glasses containing CaO as the sole alkaline earth metal oxide can be observed in Tables IV and IVA where, on a cation percent basis, the glasses contain equal quantities of CaO and SrO.
TABLE IV
______________________________________
18 19 20 21
______________________________________
SiO.sub.2
58.2 57.0 58.1 57.0
CaO 12.7 12.5 10.6 10.4
SrO 23.5 23.1 19.6 19.2
ZnO -- -- 6.15 6.03
Na.sub.2 O
2.11 2.07 2.11 2.07
Al.sub.2 O.sub.3
1.15 1.14 1.15 1.14
F 1.95 3.84 1.95 3.84
mg/cm.sup.2
0.42 0.43 0.10 0.08
Cry. Liq.
1300 1325 1334 1370
______________________________________
TABLE IVA
______________________________________
18 19 20 21
______________________________________
SiO.sub.2 62.74 61.54 62.74
61.53
CaO 14.71 14.42 12.26
12.02
SrO 14.71 14.42 12.26
12.02
ZnO -- -- 4.90 4.81
Na.sub.2 O 4.41 4.33 4.41 4.33
Al.sub.2 O.sub.3
1.47 1.44 1.47 1.44
F 1.96 3.85 1.96 3.85
______________________________________
Tables V and VA indicate that high levels of ZnO enhance the resistance of the glasses to alkali attack even at relatively low SiO2 values. Moreover, in glasses containing such low levels of SiO2, ZnO not only improves the alkali resistance thereof but also the density of opacity. Nevertheless, it must be noted that the inclusion of fluoride in glasses of low silica contents deleteriously affects the alkali resistance of such glasses even when high levels of ZnO are present.
TABLE V
______________________________________
22 23 24
______________________________________
SiO.sub.2
54.2 51.1 53.2
CaO 26.7 12.3 26.1
ZnO 19.0 36.5 18.6
F -- -- 1.96
mg/cm.sup.2
0.10 0.03 0.20
Op. Den. Clear Dense Dense
______________________________________
TABLE VA
______________________________________
22 23 24
______________________________________
SiO.sub.2
56.0 56.0 54.9
CaO 29.5 14.5 14.2
ZnO 14.5 29.5 28.9
F -- -- 2.0
______________________________________
Tables VI and VIA illustrate the flexibility available in adjusting the content of alkali metal and/or alkaline earth metal to increase the coefficient of thermal expansion of the glass with minimal effect upon alkali resistance. For example, a slight increase in the level of CaO at the expense of SiO2 raises the expansion coefficient with only a slight reduction in alkali resistance. Unfortunately, a concomitant effect is a sacrifice in the density of the opacity. Opal density can be restored, however, through the addition of fluoride. And because of the high SiO2 contents of the glasses, this addition of fluoride does not have a markedly adverse effect upon alkali resistance.
TABLE VI
__________________________________________________________________________
12 25 26 27 28 29 30
__________________________________________________________________________
SiO.sub.2
66.5 64.5
61.6
59.8
65.8 64.7
62.8
CaO 23.9 25.8
28.7
27.9
24.0 24.2
23.5
ZnO 6.93
6.94
6.9
6.7
6.96
7.0
6.8
Na.sub.2 O
2.64
2.64
2.65
2.57
3.18
4.0
3.89
F -- -- -- 2.91
-- -- 2.94
mg/cm.sup.2
0.05 0.07
-- 0.06
0.05
-- 0.06
Op. Den.
Dense
Dense
Clear
Dense
Medium
Light
Dense
Exp. 67 70 -- 76.1
70 -- 73.2
__________________________________________________________________________
TABLE VIA
______________________________________
12 25 26 27 28 29 30
______________________________________
SiO.sub.2
65.0 63.0 60.0 58.3 64.0 62.5 60.7
CaO 25.0 27.0 30.0 29.1 25.0 25.0 24.3
ZnO 5.0 5.0 5.0 4.9 5.0 5.0 4.9
Na.sub.2 O
5.0 5.0 5.0 4.9 6.0 7.5 7.3
F -- -- -- 2.8 -- -- 2.8
______________________________________
Tables VII and VIIA and Tables VIII and VIIIA provide further illustrations of varying the alkali metal contents of the glasses to yield articles of acceptable resistance to alkalies. For example, Li2 O can replace part of the SiO2 without undue reduction in alkali resistance. K2 O can be utilized as part of the alkali metal content and its use appears to enhance the alkali resistance of the glass. Nevertheless, its effect upon phase separation is very profound such that the restoration of opacity demands greater fluoride levels than are desirable.
TABLE VII
______________________________________
31 32 33
______________________________________
SiO.sub.2 66.5 66.0 65.4
CaO 22.9 24.1 23.3
ZnO 6.92 6.98 7.03
Na.sub.2 O
2.37 1.06 2.41
Li.sub.2 O
-- 0.71 0.52
Al.sub.2 O.sub.3
1.30 1.09 1.32
mg/cm.sup.2
0.01 0.05 0.05
Cry. Liq. 1410 1420 1370
Op. Den. Dense Dense Dense
______________________________________
TABLE VIIA
______________________________________
31 32 33
______________________________________
SiO.sub.2 65.0 64.0 63.0
CaO 24.0 25.0 24.0
ZnO 5.0 5.0 5.0
Na.sub.2 O
4.5 2.0 4.5
Li.sub.2 O
-- 2.75 2.0
Al.sub.2 O.sub.3
1.5 1.25 1.5
______________________________________
Substituting CaO for Na2 O has no significant deleterious effect. Replacing a small amount of CaO with SiO2 does not appear to improve alkali resistance, whereas substituting SiO2 for Na2 O significantly enhances alkali resistance.
TABLE VIII
______________________________________
12 34 35 36
______________________________________
SiO.sub.2 66.5 66.0 68.4 67.5
CaO 23.9 25.1 21.9 23.7
ZnO 6.93 6.88 6.91 6.87
Na.sub.2 O 2.64 1.83 2.63 1.83
mg/cm.sup.2 0.05 0.07 0.06 0.01
______________________________________
TABLE VIIIA
______________________________________
12 34 35 36
______________________________________
SiO.sub.2 65.0 65.0 67.0 66.5
CaO 25.0 26.5 23.0 25.0
ZnO 5.0 5.0 5.0 5.0
Na.sub.2 O 5.0 3.5 5.0 3.5
______________________________________
Tables IX and IXA show that replacing CaO with ZnO causes a reduction in the coefficient of thermal expansion of the glass as well as improving the alkali resistance thereof as has been illustrated above.
TABLE IX
______________________________________
37 38 35
______________________________________
SiO.sub.2 67.3 67.8 68.4
CaO 17.8 19.8 21.9
ZnO 12.23 9.6 6.91
Na.sub.2 O
2.59 2.61 2.63
mg/cm.sup.2
0.03 0.04 0.06
Exp. 59.1 60.9 64.1
______________________________________
TABLE IXA
______________________________________
37 38 35
______________________________________
SiO.sub.2
67.0 67.0 67.0
CaO 19.0 21.0 23.0
ZnO 9.0 7.0 5.0
Na.sub.2 O
5.0 5.0 5.0
______________________________________
Tables X and XA disclose that a small amount of Al2 O3 can lead to a marked improvement in alkali resistance. For example, a comparison of Example 39 with Example 40 clearly evidences a significant improvement in alkali resistance when Al2 O3 is substituted for SiO2. A similar effect occurs when Al2 O3 replaces some SiO2 and alkali metal oxide, as is demonstrated through a comparison of Example 41 with Example 39. Examples 12 and 31 manifest a fivefold reduction in weight loss when Al2 O3 is substituted for Na2 O and CaO, and the SiO2 value is maintained constant.
TABLE X
______________________________________
39 40 12 41 31
______________________________________
SiO.sub.2
65.3 64.0 66.5 64.4 66.5
CaO 19.7 19.8 23.9 19.7 22.9
ZnO 12.25 12.29 6.93 12.26
6.92
Na.sub.2 O
2.59 2.60 2.64 2.34 2.37
Al.sub.2 O.sub.3
-- 1.28 -- 1.28 1.30
mg/cm.sup.2
0.05 <0.01 0.05 0.02 0.01
Op. Liq. -- -- -- -- 1140
______________________________________
TABLE XA
______________________________________
39 40 12 41 31
______________________________________
SiO.sub.2
65.0 63.5 65.0 64.0 65.0
CaO 21.0 21.0 25.0 21.0 24.0
ZnO 9.0 9.0 5.0 9.0 5.0
Na.sub.2 O
5.0 5.0 5.0 4.5 4.5
Al.sub.2 O.sub.3
-- 1.5 -- 1.5 1.5
______________________________________
Tables XI and XIA are designed to demonstrate the correlation which exists between the weight loss measurements and the above-described detergent test. Thus, glasses exhibiting a weight loss of 0.08 mg/cm2 will sometimes demonstrate an "A" rating in the stain test. The loss of gloss observed on the top surface of the samples and the retention of gloss seen on the bottom surface of the samples can be explained in the following manner. The bottom refers to the surface of the sample which contacts the steel plate onto which the melt is poured to form glass patties. This surface is analogous to and would be expected to manifest properties similar to those noted on the surface of glass articles formed via a pressing operation. In contrast, the top surface cools slowly and is conjectured to have associated with it an exceptionally coarse phase separation. For whatever reason, the top surface exhibits a misleading high tendency to lose its gloss during the detergent test. The assumption that the bottom surface of the sample is the better indicator of properties is indicated by Example 46. Hence, discs pressed from a melt of that glass displayed no loss of gloss in spite of its similarity in composition to Example 42. In sum, glasses demonstrating a weight loss of no more than about 0.1 mg/cm2 are reasonably likely to pass the detergent test where pressed articles are utilized. The samples were subjected to the stain test for 96 hours except where noted otherwise. Likewise, the gloss condition reflects a 96-hour immersion in detergent except where noted otherwise. "Top" refers to the top surface of the sample and "bottom" to the obverse surface. "Yes" indicates a significant loss of gloss whereas "no" signifies an essentially unchanged surface.
TABLE XI
______________________________________
42 43 44 45 46 47
______________________________________
SiO.sub.2
62.3 65.0 65.5 64.8 60.0 58.1
CaO 17.9 19.6 19.3 19.1 15.1 10.6
ZnO 6.49 6.77 6.82 6.75 9.37 6.15
Na.sub.2 O
2.22 2.32 1.56 1.54 2.14 2.11
Al.sub.2 O.sub.3
1.22 1.28 1.28 1.27 1.17 1.15
Li.sub.2 O
-- -- 0.50 0.50 -- --
MgO -- 0.68 0.68 0.67 -- --
SrO -- 1.72 1.74 1.72 -- 19.6
BaO 9.8 2.56 2.57 2.54 9.42 0.28
F -- -- -- 0.99 2.78 1.95
mg/cm.sup.2
0.08 0.06 0.06 0.06 * 0.10
Stain A A A A A **
Gloss
Top Yes Yes Yes Yes No Yes
Bottom No No No No No Yes
______________________________________
*Pressed disc. No weight loss data obtained. By analogy to Example 42
estimated to be about 0.05 mg/cm.sup.2.
**Test run only 24 hours because of severe loss of gloss.
TABLE XIA
______________________________________
42 43 44 45 46 47
______________________________________
SiO.sub.2
65.0 65.0 65.0 64.45 63.11
62.76
CaO 20.0 21.0 20.5 20.3 16.99
12.25
ZnO 5.0 5.0 5.0 4.95 7.28 4.90
Na.sub.2 O
4.5 4.5 3.0 2.97 4.37 4.41
Al.sub.2 O.sub.3
1.5 1.5 1.5 1.49 1.46 1.47
Li.sub.2 O
-- -- 2.0 1.98 -- --
MgO -- 1.0 1.0 0.99 -- --
SrO -- 1.0 1.0 0.99 -- 12.25
BaO 4 1.0 1.0 0.99 3.88 --
F -- -- -- 0.99 2.91 1.96
______________________________________
Tables XII and XIIA illustrate studies undertaken to investigate means for achieving a lower crystal liquidus temperature in the subject glasses without harming the alkali resistance thereof. The exemplary compositions reported demonstrate the effect resulting from mixing the alkaline earth metal oxides. As is evident, any decrease in liquidus temperature attributed to the entropy of mixing, when the alkaline earth metal oxides are combined, is virtually negligible compared to the direct influence of the ionic size of the individual alkaline earth metals. It should also be noted that the viscosity of the glasses tends to become independent of composition at very high temperatures. Consequently, any change in composition which reduces the liquidus temperature automatically increases the viscosity of the glass at the liquidus. Example 52 exhibits a desirably low liquidus temperature and high liquidus viscosity but, unfortunately, has unsatisfactory alkali resistance. ZnO can be added to improve alkali resistance but, as manifested in Table IV above, ZnO raises the liquidus temperature.
TABLE XII
__________________________________________________________________________
48 49 50 51 52 53 54
__________________________________________________________________________
SiO.sub.2
67.8 66.3 63.6 65.0 60.1 68.8 62
MgO 0.12 0.10 0.06 0.10 0.05 3.55 0.10
CaO 29.2 23.8 13.7 23.4 13.0 24.7 22.4
SrO -- -- -- 8.63 23.9 0.02 0.02
BaO -- -- -- 0.12 0.34 -- 12.3
ZnO -- 6.91 19.88
-- -- -- --
Na.sub.2 O
2.4 2.37 2.27 2.32 2.15 2.46 2.23
Al.sub.2 O.sub.3
0.44 0.43 0.42 0.42 0.40 0.45 0.41
Cry. Liq.
1380 1430 1475 1347 1245 1415 1290
Viscosity
At Liq.
100 80 -- 140 400 100 200
At 1430° C.
65 80 -- 55 52 80 80
S.P. 832 800 786 828 817 825 813
__________________________________________________________________________
TABLE XIIA
______________________________________
48 49 50 51 52 53 54
______________________________________
SiO.sub.2
64.9 64.9 64.9 64.9 64.8 65.0 64.9
MgO 0.2 0.1 0.1 0.1 0.1 5.0 0.1
CaO 29.9 25.0 15.0 24.9 15.0 25.0 25.0
SrO -- -- -- 5.0 15.0 -- --
BaO -- -- -- -- 0.1 -- 5.0
ZnO -- 5.0 15.0 -- -- -- --
Na.sub.2 O
4.5 4.5 4.5 4.5 4.5 4.5 4.5
Al.sub.2 O.sub.3
0.5 0.5 0.5 0.5 0.5 0.5 0.5
______________________________________
Tables XIII and XIIIA point out that not only does the substitution of TiO2 for SiO2 not reduce the crystal liquidus temperature, but also that the substitution introduces color into the opal glass. The replacement of SiO2 with B2 O3 or P2 O5 does not appear to endow the final glass with any advantageous properties.
TABLE XIII
__________________________________________________________________________
55 56 57 58 59 60 12
__________________________________________________________________________
SiO.sub.2
66.4 61.5 63.9 60.9 60.8 63.4 66.5
CaO 23.8 23.5 23.7 17.8 23.3 24.3 23.9
ZnO 6.92 6.83 6.88 6.45 6.75 7.04 6.93
Na.sub.2 O
2.50 2.47 2.49 2.33 2.44 2.55 2.64
TiO.sub.2
-- 5.36 2.70 2.53 -- -- --
Al.sub.2 O.sub.3
0.22 0.21 0.24 0.20 1.91 0.20 --
BaO -- -- -- 9.72 -- -- --
P.sub.2 O.sub.5
-- -- -- -- 2.36 -- --
B.sub.2 O.sub.3
-- -- -- -- -- 2.41 --
Color
White
Purple
Tan Tan White
White
White
Cry. Liq.
1420 -- 1415 1370 1355 1370 1300
Gloss
Top -- -- -- -- Yes* Yes* Yes**
Bottom
-- -- -- -- Yes* Yes* No
__________________________________________________________________________
*Test run only 24 hours because of severe loss of gloss.
**Poured patty surface. No loss of gloss with pressed discs.
TABLE XIIIA
______________________________________
55 56 57 58 59 60 12
______________________________________
SiO.sub.2
65.0 61.0 62.0 64.0 61.0 61.0 65.0
CaO 25.0 25.0 25.0 20.0 25.0 25.0 25.0
ZnO 5.0 5.0 5.0 5.0 5.0 5.0 5.0
Na.sub.2 O
4.75 4.75 4.75 4.75 4.75 4.75 5.0
TiO.sub.2
-- 4.0 2.0 2.0 -- -- --
Al.sub.2 O.sub.3
0.25 0.25 0.25 0.25 0.25 0.25 --
BaO -- -- -- 4.0 -- -- --
P.sub.2 O.sub.5
-- -- -- -- 2.0 -- --
B.sub.2 O.sub.3
-- -- -- -- -- 4.0 --
______________________________________
Whereas laboratory experience has indicated that very useful products can be secured from glasses consisting essentially of CaO, ZnO, and SiO2 with, optionally, Na2 O, Al2 O3, and/or F, the above Examples clearly indicate that minor additions of numerous compatible metal oxides are possible with little adverse and sometimes advantageous effects. Conventional glass colorants may also be included, if desired. The total of all such additions will desirably be held below about 10% by weight, however, except for SrO which may be included in levels up to about 20% by weight. Based upon all around property considerations, the more preferred glasses will consist essentially, expressed in terms of weight percent on the oxide basis, of 60-70% SiO2, 20-30% CaO, 5-15% ZnO, 1.5-4% Na2 O, 0-2% Al2 O3, and 0-3% F. Example 12 is deemed to be the most preferred composition. Electron micrographs of that glass in the opal state demonstrate that spherical amorphous droplets no larger than about 0.5 micron impart the opacity. Such small droplets will not constitute stress concentrating sites. Inasmuch as the alkali metal content of the inventive glasses is low, products made therefrom are quite useful in microwave applications.
Claims (3)
1. A spontaneous opal glass having a softening point in excess of 750° C., a coefficient of thermal expansion between about 60-90×10-7 /°C., a crystal liquidus temperature below 1350° C., a viscosity at the liquidus temperature of at least 200 poises, excellent resistance to attack by alkalies, and wherein spherically-shaped, glassy droplets constitute the opal phase, said glass consisting essentially, expressed in terms of weight percent on the oxide basis, of about
______________________________________
SiO.sub.2
50-72 Na.sub.2 O
0-8
CaO 10-40 Al.sub.2 O.sub.3
0-2
ZnO 4-40 F 0-5
______________________________________
2. A spontaneous opal glass according to claim 1 also containing up to 20% SrO.
3. A spontaneous opal glass according to claim 1 consisting essentially, expressed in terms of weight percent on the oxide basis, of
______________________________________
SiO.sub.2
60-70 Na.sub.2 O
1.5-4
CaO 20-30 Al.sub.2 O.sub.3
0-2
ZnO 5-15 F 0-3
______________________________________
Priority Applications (1)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| US06/500,565 US4439528A (en) | 1983-06-02 | 1983-06-02 | Spontaneous opal glass compositions |
Applications Claiming Priority (1)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| US06/500,565 US4439528A (en) | 1983-06-02 | 1983-06-02 | Spontaneous opal glass compositions |
Publications (1)
| Publication Number | Publication Date |
|---|---|
| US4439528A true US4439528A (en) | 1984-03-27 |
Family
ID=23989976
Family Applications (1)
| Application Number | Title | Priority Date | Filing Date |
|---|---|---|---|
| US06/500,565 Expired - Lifetime US4439528A (en) | 1983-06-02 | 1983-06-02 | Spontaneous opal glass compositions |
Country Status (1)
| Country | Link |
|---|---|
| US (1) | US4439528A (en) |
Cited By (7)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| EP0917135A1 (en) * | 1997-06-05 | 1999-05-19 | Hoya Corporation | Substrate for information recording media |
| EP0953548A1 (en) * | 1997-07-30 | 1999-11-03 | Hoya Corporation | Method of producing glass substrate for information recording medium |
| US6277777B1 (en) | 1999-08-03 | 2001-08-21 | Johns Manville International, Inc. | Boron-free glass composition and filtration media |
| DE102005000663A1 (en) * | 2005-01-04 | 2006-11-09 | Schott Ag | Process for clouding a glass, in particular a borosilicate glass and lamps with a haze |
| US9240568B2 (en) | 2011-11-10 | 2016-01-19 | Corning Incorporated | Opal glasses for light extraction |
| US10505129B2 (en) * | 2016-04-28 | 2019-12-10 | Schott Ag | Method of production of high-refractive thin glass substrates |
| CN112251787A (en) * | 2020-08-26 | 2021-01-22 | 西安交通大学 | Preparation method of zinc calcium silicate nano-array bioactive coating |
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| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| US3275492A (en) * | 1961-02-03 | 1966-09-27 | Loing Verreries | Opal glass with a low coefficient of thermal expansion |
| US3661601A (en) * | 1969-03-21 | 1972-05-09 | Corning Glass Works | Opal glass compositions |
| US3681098A (en) * | 1970-01-14 | 1972-08-01 | Corning Glass Works | Opal glass compositions comprising calcium fluoride |
| GB1315828A (en) * | 1970-11-27 | 1973-05-02 | Jobling & Co James A | Production of opal glass |
| US4311529A (en) * | 1980-06-17 | 1982-01-19 | Corning Glass Works | Tinted opal glass |
| US4323653A (en) * | 1981-04-16 | 1982-04-06 | Corning Glass Works | Inhibiting crystallization of opal glass compositions |
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| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| US3275492A (en) * | 1961-02-03 | 1966-09-27 | Loing Verreries | Opal glass with a low coefficient of thermal expansion |
| US3661601A (en) * | 1969-03-21 | 1972-05-09 | Corning Glass Works | Opal glass compositions |
| US3681098A (en) * | 1970-01-14 | 1972-08-01 | Corning Glass Works | Opal glass compositions comprising calcium fluoride |
| GB1315828A (en) * | 1970-11-27 | 1973-05-02 | Jobling & Co James A | Production of opal glass |
| US4311529A (en) * | 1980-06-17 | 1982-01-19 | Corning Glass Works | Tinted opal glass |
| US4323653A (en) * | 1981-04-16 | 1982-04-06 | Corning Glass Works | Inhibiting crystallization of opal glass compositions |
Cited By (12)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| EP0917135A1 (en) * | 1997-06-05 | 1999-05-19 | Hoya Corporation | Substrate for information recording media |
| EP0917135A4 (en) * | 1997-06-05 | 1999-12-15 | Hoya Corp | Substrate for information recording media |
| EP0953548A1 (en) * | 1997-07-30 | 1999-11-03 | Hoya Corporation | Method of producing glass substrate for information recording medium |
| EP0953548A4 (en) * | 1997-07-30 | 1999-12-22 | Hoya Corp | Method of producing glass substrate for information recording medium |
| US6277777B1 (en) | 1999-08-03 | 2001-08-21 | Johns Manville International, Inc. | Boron-free glass composition and filtration media |
| DE102005000663A1 (en) * | 2005-01-04 | 2006-11-09 | Schott Ag | Process for clouding a glass, in particular a borosilicate glass and lamps with a haze |
| DE102005000663B4 (en) * | 2005-01-04 | 2010-08-05 | Schott Ag | Process for clouding a glass, in particular a borosilicate glass, glass tube and its use |
| US9240568B2 (en) | 2011-11-10 | 2016-01-19 | Corning Incorporated | Opal glasses for light extraction |
| US9496521B2 (en) | 2011-11-10 | 2016-11-15 | Corning Incorporated | Opal glasses for light extraction |
| US10505129B2 (en) * | 2016-04-28 | 2019-12-10 | Schott Ag | Method of production of high-refractive thin glass substrates |
| CN112194349A (en) * | 2016-04-28 | 2021-01-08 | 肖特股份有限公司 | Method for producing high-refraction thin glass substrate |
| CN112251787A (en) * | 2020-08-26 | 2021-01-22 | 西安交通大学 | Preparation method of zinc calcium silicate nano-array bioactive coating |
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